Introduction

The STM32F303VCT6 is a powerful ARM Cortex-M4 microcontroller from STMicroelectronics, equipped with a wide array of features, including integrated analog-to-digital converters (ADC), timers, communication interfaces like SPI, I2C, and UART, and a high-performance CPU that can run at speeds of up to 72 MHz. These features make the STM32F303VCT6 an excellent choice for a wide variety of DIY electronic projects, ranging from basic sensors to more complex applications like home automation and data logging.

In this project, we will design and build a smart weather station using the STM32F303VCT6. The station will measure key environmental parameters, such as temperature, humidity, and atmospheric pressure, and display the results on an LCD screen. Additionally, the system will log the collected data to an SD card for later review and analysis. This project combines multiple key aspects of embedded systems: sensor interfacing, data processing, user interaction, and data storage.

This tutorial will walk you through all the steps to create the weather station, from hardware setup and wiring to software programming, with an emphasis on utilizing the STM32F303VCT6.

Components Required

Before diving into the project, let’s look at the components we will use:

1) STM32F303VCT6 Microcontroller: This will be the brain of our weather station, handling all sensor readings, data processing, and communication.

2) DHT22 Temperature and Humidity Sensor: A widely-used sensor for measuring temperature and humidity.

3) BMP180 Barometric Pressure Sensor: An I2C-based sensor for measuring atmospheric pressure.

4) 16x2 LCD Display (I2C): To display temperature, humidity, and pressure readings.

5) MicroSD Card Module: To log the weather data for future analysis.

6) Push Buttons: To reset the system or navigate through the menus.

7) Resistors, Capacitors, and Jumper Wires: For circuit assembly.

8) Breadboard: For assembling the project.

9) 5V Power Supply: To power the microcontroller and sensors.

Project Overview

1) The main objective of this project is to build a smart weather station that:

2) Measures the temperature, humidity, and atmospheric pressure using the DHT22 and BMP180 sensors.

3) Displays these readings in real-time on a 16x2 LCD display.

4) Logs the weather data on an SD card for long-term storage.

5) Allows the user to interact with the system using push buttons for resetting or viewing different data logs.

Step-by-Step Build

1. Setting Up the STM32F303VCT6

The STM32F303VCT6 is a powerful microcontroller with many features, making it ideal for this type of project. It has integrated ADCs, which we will use to interface with analog sensors. The microcontroller also supports several communication protocols, including I2C, which is essential for connecting the DHT22, BMP180 sensors, and the SD card module.

Programming Environment Setup: First, set up the development environment for the STM32F303VCT6. The best tools for programming STM32 microcontrollers are:

STM32CubeIDE: An Integrated Development Environment (IDE) for STM32 microcontrollers, which includes STM32CubeMX for configuring peripherals.

ST-Link/V2 Debugger: A hardware debugger for programming the STM32F303VCT6.

Configure the Microcontroller: Use STM32CubeMX to configure the microcontroller’s GPIO pins, I2C, and SPI interfaces, as well as the clock settings. Here’s a breakdown of the essential configurations:

1) Configure I2C for communication with the DHT22 and BMP180 sensors.

2) Configure SPI or SDIO for interfacing with the SD card.

3) Set up GPIO pins for interfacing with the push buttons and controlling the LCD display.

4) Peripheral Initialization: Once the STM32CubeMX configuration is done, generate the initialization code and open it in STM32CubeIDE.

2. Wiring the Components

Now that the STM32F303VCT6 is configured, it’s time to wire the components.

DHT22 Temperature and Humidity Sensor:

· The DHT22 uses a single-wire data protocol, so it will be connected to a GPIO pin of the STM32F303VCT6.

1) VCC → 3.3V

2) GND → GND

3) Data → GPIO pin of STM32F303VCT6 (configured in CubeMX)

BMP180 Barometric Pressure Sensor:

1) The BMP180 uses I2C for communication, so we will connect it to the I2C lines.

2) VCC → 3.3V

3) GND → GND

4) SDA → I2C data pin (STM32F303VCT6)

5) SCL → I2C clock pin (STM32F303VCT6)

6) 16x2 LCD Display (I2C):

7) The LCD display will also use I2C for communication.

8) VCC → 5V

9) GND → GND

10) SDA → I2C data pin (STM32F303VCT6)

11) SCL → I2C clock pin (STM32F303VCT6)

12) MicroSD Card Module:

13) The SD card will typically use SPI communication.

14) MISO, MOSI, SCK, CS → SPI pins (configured in CubeMX)

15) VCC → 5V

16) GND → GND

17) Push Buttons:

18) These will be connected to GPIO pins, typically with pull-up resistors.

19) Button 1 → GPIO pin for reset

20) Button 2 → GPIO pin for navigating data logs

3. Writing the Code

Now that the hardware is set up, let’s dive into the software development. Below is an outline of the key steps involved in writing the firmware for this project.

3.1 Sensor Data Acquisition

1) DHT22: The DHT22 sensor communicates using a single-wire interface. You can either write a custom driver to handle the protocol or use an existing library. The sensor provides temperature and humidity data as a 40-bit digital value, which we can easily process in the STM32F303VCT6.

2) BMP180: The BMP180 is an I2C sensor that provides data in two formats: temperature and pressure. To interface with the BMP180, use the STM32's I2C functions to read the temperature and pressure data.

3) 3.2 Displaying Data on the LCD

4) The LCD will display the current temperature, humidity, and pressure readings in real-time. Using the I2C LCD library, we can write values to the screen.

c

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// Display temperature on the LCD
sprintf(buffer, "Temp: %.2f C", temperature);
LCD_DisplayString(buffer);

// Display humidity on the LCD
sprintf(buffer, "Humidity: %.2f %%", humidity);
LCD_DisplayString(buffer);

// Display pressure on the LCD
sprintf(buffer, "Pressure: %.2f hPa", pressure);
LCD_DisplayString(buffer);

3.3 Logging Data to the SD Card

The SD card module uses SPI to communicate with the STM32F303VCT6. We will use the FatFS library, a popular library for SD card file systems, to log data to the SD card.

• Initialize the SPI interface for SD card communication.
• Use f_open(), f_write(), and f_close() to store data to a file on the SD card.

c

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FATFS fs;
FIL file;
f_mount(&fs, "", 0);
f_open(&file, "weather_log.txt", FA_WRITE | FA_OPEN_ALWAYS);
f_printf(&file, "Temp: %.2f C, Humidity: %.2f %%\n", temperature, humidity);
f_close(&file);

3.4 User Interaction with Push Buttons

We will implement basic user interaction with push buttons. For example, one button could trigger a data reset, while another could cycle through different data logs.

c

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if (button_pressed()) {
  // Reset the system or cycle through the data
  reset_system();
}

3.5 Main Program

In the main program loop, we will continuously read sensor data, display it on the LCD, and log it to the SD card at regular intervals.

c

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int main(void)
{
  HAL_Init();
  SystemClock_Config();
  
  // Initialize peripherals
  MX_GPIO_Init();
  MX_I2C1_Init();
  MX_SPI1_Init();
  MX_LCD_Init();
  
  // Initialize sensors
  DHT22_Init();
  BMP180_Init();
  
  while (1)
  {
    // Read data from sensors
    float temperature = DHT22_ReadTemperature();
    float humidity = DHT22_ReadHumidity();
    float pressure = BMP180_ReadPressure();
    
    // Display data on LCD
    display_on_LCD(temperature, humidity, pressure);
    
    // Log data to SD card
    log_data_to_SD(temperature, humidity, pressure);
    
    // Delay between readings
    HAL_Delay(2000);
  }
}

4. Testing the System

Once the hardware is set up and the firmware is written, it’s time to test the weather station. Power up the system, and check the LCD display for real-time readings. Press the buttons to test user interaction and verify that the data is being logged to the SD card.

You can open the SD card and inspect the weather_log.txt file to confirm that the data is being stored correctly.

Conclusion

In this project, we built a smart weather station using the STM32F303VCT6 microcontroller. We successfully interfaced with temperature, humidity, and pressure sensors (DHT22 and BMP180), displayed real-time data on an LCD, and logged the data to an SD card for later analysis. By using STM32CubeMX, STM32CubeIDE, and various libraries, we were able to focus on the core components of the project and ensure a clean and efficient design.

This project serves as an excellent introduction to using STM32 microcontrollers for sensor-based projects, interfacing with I2C and SPI devices, and working with data storage. You can extend this project by adding more sensors, connecting it to the internet for remote monitoring, or building a mobile app to display the weather data in real-time. The possibilities are endless!